1. Field of the Invention
This invention relates to a process for preparing polyol blends. It involves delayed co-initiation whereby a second initiator is added to the reaction vessel after a first initiator has reached the specified equivalent weight.
2. Description of the Prior Art
It is well known to prepare polyurethane products by the reaction of an organic polyisocyanate and a polyol such as a polyoxyalkylene polyether polyol. Such polyols are prepared by reacting an initiator containing two or more active hydrogen atoms as determined by the Zerewittinoff method with an epoxide, preferably an alkylene oxide. Generally the reaction between the organic polyisocyanate and polyol is carried out in the presence of a blowing agent, catalyst, and other well known ingredients.
It is also known that polyol blends can be used to vary the properties of the polyol (such as viscosity) and/or the polyurethane products. The problem with using blends, however, is that they are expensive to make because of the time and energy involved in mechanically blending the individual polyols to form the blend.
It is also known to prepare polyol blends by simultaneously reacting two or more initiators (co-initiation process) with an epoxide to form a polyol blend. This eliminates the need for mechanical blending and thereby reduces the cost of manufacturing the polyol.